TY - BOOK

T1 - Fjord sediments in Greenland

T2 - A climate archive at the intersection between the ocean and the ice sheet

AU - Wangner, David Johannes

PY - 2019

Y1 - 2019

N2 - In recent years, the Greenland Ice Sheet has experienced persistent mass loss, contributing significantly to global sea level rise. About a third of this mass loss is attributed to dynamical discharge via marine terminating glaciers. In order to understand the current processes better and to put these changes into a longer-term perspective it is important to study past environmental conditions and the glacier response to them. In this thesis, marine sediment cores from five different fjords in West- and South-East Greenland were investigated to determine the dynamics of marine terminating glaciers in response to ocean temperature variability. The annual deposition of iceberg rafted debris was used to gain understanding of glaciological change, such as iceberg productivity, margin changes and margin type (calving or floating glacier). Ocean temperature was reconstructed using either benthic foraminifera assemblages or alkenone based paleo-thermometry. In West Greenland, the studies reconstructing ocean and glacier change of the last 2000 years in Disko Bugt, and the last 100 years in Upernavik Isfjord, reveal a link between bottom water temperature within the West Greenland Current and glacier stability of Jakobshavn Isbræ and Upernavik Glacier, respectively. Moreover, a lack of IRD sedimentation in Disko Bugt between 1500 to 1850 CE indicates the development of a floating glacier tongue at Jakobshavn Isbræ during the Little Ice Age. In South-East Greenland, the study reconstructing the last 2000 years of ocean and glacier change in Sermilik Fjord shows relatively minor changes in IRD sedimentation from Helheim Glacier, although SSTs warmed significantly during the Little Ice Age. Besides persistent sea-ice, this was again linked to the existence of a floating glacier tongue. At the onset of the 20th century SSTs raised and Helheim and Kangerlugssuaq glaciers responded with ice tongue collapses. In contrast to that, the study of Thrym Glacier by Nørre Skjoldungesund shows limited response to similar changes in SSTs, which was mostly linked to its glacier configuration limiting ice-ocean interaction. Furthermore, this thesis also discusses the applicability of established proxies, such as alkenone paleothermometry, foraminifera assemblage and IRD, in complex fjord systems of Greenland. A focus on observations of the processes behind of these proxies in the present day environment may help to reduce uncertainties in the interpretation of the longer-term data set.

AB - In recent years, the Greenland Ice Sheet has experienced persistent mass loss, contributing significantly to global sea level rise. About a third of this mass loss is attributed to dynamical discharge via marine terminating glaciers. In order to understand the current processes better and to put these changes into a longer-term perspective it is important to study past environmental conditions and the glacier response to them. In this thesis, marine sediment cores from five different fjords in West- and South-East Greenland were investigated to determine the dynamics of marine terminating glaciers in response to ocean temperature variability. The annual deposition of iceberg rafted debris was used to gain understanding of glaciological change, such as iceberg productivity, margin changes and margin type (calving or floating glacier). Ocean temperature was reconstructed using either benthic foraminifera assemblages or alkenone based paleo-thermometry. In West Greenland, the studies reconstructing ocean and glacier change of the last 2000 years in Disko Bugt, and the last 100 years in Upernavik Isfjord, reveal a link between bottom water temperature within the West Greenland Current and glacier stability of Jakobshavn Isbræ and Upernavik Glacier, respectively. Moreover, a lack of IRD sedimentation in Disko Bugt between 1500 to 1850 CE indicates the development of a floating glacier tongue at Jakobshavn Isbræ during the Little Ice Age. In South-East Greenland, the study reconstructing the last 2000 years of ocean and glacier change in Sermilik Fjord shows relatively minor changes in IRD sedimentation from Helheim Glacier, although SSTs warmed significantly during the Little Ice Age. Besides persistent sea-ice, this was again linked to the existence of a floating glacier tongue. At the onset of the 20th century SSTs raised and Helheim and Kangerlugssuaq glaciers responded with ice tongue collapses. In contrast to that, the study of Thrym Glacier by Nørre Skjoldungesund shows limited response to similar changes in SSTs, which was mostly linked to its glacier configuration limiting ice-ocean interaction. Furthermore, this thesis also discusses the applicability of established proxies, such as alkenone paleothermometry, foraminifera assemblage and IRD, in complex fjord systems of Greenland. A focus on observations of the processes behind of these proxies in the present day environment may help to reduce uncertainties in the interpretation of the longer-term data set.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/1pioq0f/alma99123532513105763

M3 - Ph.D. thesis

BT - Fjord sediments in Greenland

PB - Natural History Museum of Denmark, Faculty of Science, University of Copenhagen

ER -